https://uvadoc.uva.es/handle/10324/1272 Dpto. Electricidad y Electrónica - Comunicaciones a congresos, conferencias, etc. 2026-04-08T22:54:03Z https://uvadoc.uva.es/handle/10324/80036 Magnon propagation in antiferromagnetic (AFM) and/or ferrimagnetic (FiM) insulators is drawing attention due to the benefits as opposed to their ferromagnetic (FM) counterparts, such as higher fundamental frequency and insensitivity to external magnetic field perturbations. Spin wave (SW) propagation in these materials connects magnonics with spintronics, since spin current is mainly transported by magnons. A comprehensive study of the transmission of SWs in bent waveguides made of FiM material is made here. SWs are promoted by spin currents at one end of the guide and their transmission is measured at the other end. Current frequency is chosen to excite a single wavelength λ according to forward volume spin wave (FVSW) propagation dispersion curves. The guide has two bends at its center forming a certain angle and are distant a length apart. Both the angle and the distance are determinants on the transmission coefficient τ of the SW, defined from the quotient between the amplitude of the SW at the measurement point and the amplitude at a point at the same distance as the measurement point with respect to the excitation point in a strip without bends, i.e., without reflections associated with the geometry. Transmission minima and maxima are found for the different lengths between bends considered which coincide respectively with lengths equal to multiples of λ/2 and odd multiples of λ/4 , which is reminiscent of interferometry results for other types of guided waves, although in this case they are only explainable through an imaginary reflection coefficient at both bends. 2025-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/66550 We studied epitaxial growth of Ge films on Si(001) 2×1 at different temperatures using classical molecular dynamics simulations. Ge-Si intermixing contributes to strain accommodation mostly in the original Si substrate surface and first grown Ge layer. Stress accumulation is further released by the generation of dislocations whose amount and type depend on temperature. At high temperatures, a larger amount and more variety of dislocations are formed, thus affecting the surface morphology and consequently the size of 3D islands. 2023-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/66548 We used ab initio calculations to characterize PnVm(n=1−6,m=1,2) clusters in crystalline Si by calculating their formation energy, dipole moment and local vibrational modes. This information served us to discuss which PnVm complexes might be more relevant in doping during epitaxial growth or by ion implantation, and their possible behavior under microwave annealing treatments that was recently demonstrated as a promising process in technological nodes beyond 3 nm. 2023-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33903 We used classical molecular dynamics simulations to reproduce basic properties of Si, Ge and SiGe using different empirical potentials available in the literature. The empirical potential that offered the better compromise with experimental data was used to study the surface stability of these materials. We considered the (100), (100)2×1 and (111) surfaces, and we found the processing temperature range to avoid the structural degradation of studied surfaces. 2019-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33892 Electronic devices operating in harsh radiation environments must withstand high radiation levels with minimal performance degradation. Recent experiments on the radiation hardness of a new vertical p-type JFET power switch have shown a significant reduction of forward drain current under non-ionizing conditions. In this work, atomistic simulations are used to study the impact of irradiation-induced displacement damage on forward characteristics. Damage models have been updated to produce a better description of damage-dopant interactions at RT. Our results show that excess self-interstitials produced by irradiation deactivate a significant amount of B atoms, thus reducing the effective dopant concentration. 2019-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33625 Reflective surfaces (mirrors) have a wide use in the field of optical or electromagnetic applications, wherever it is needed to redirect electromagnetic radiation. Though mirror technology exists since more than 8,000 years ago, there is not yet a well-established technology for circular polarization control: even more, conventional mirrors reverse the handedness or circularly polarized waves. Bi-isotropic (chiral) structures have been proposed to manipulate the polarization of travelling waves (optical/electromagnetic activity and circular dichroism). Nevertheless, up to date, all the known examples of such materials are non-reciprocal. 2018-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33624 A bi-isotropic chiral structure has been numerically studied. It is composed of two layers of planar, 2D-chiral, honeycomb-like, parallel grids. Electromagnetic activity (gyrotropy) is observed. That leads to a strong chiral behavior with low losses. 2017-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33623 This communication presents a novel diode switchable chiral metamaterial structure that manipulates the polarization in different ways depending on the active bias lines. Three different bias states that provide three totally different behaviors have been considered: polarization rotator, circular polarization converter and linear to circular converter. 2017-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33622 Honeycomb structures have been widely used in different sectors, such as aerospace, construction,packaging, etc., due to their mechanical properties. They also have been proposed in order to use their electromagnetic properties, for example, to perform metamaterial structures. In some cases, structures, which geometrically are chiral in a two-dimensional plane, have been used too. Some authors have studied their electromagnetic behavior, in order to check whether their structural chirality translates into chiral electromagnetic behavior with negative results. 2016-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33619 A planar complementary metamaterial, as well as its corresponding inverse structure, has been designed and characterized. Numerical results (using commercial software) are presented here. The structure shows a giant gyrotropy (chirality) as well as very low losses. 2016-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/33617 A partially complementary bilayer chiral metamaterial (CMM) is proposed and numerically studied. It exhibits a strong optical activity and a small circular dichroism. The retrieval results reveal that a negative refractive index is realized in a narrow band around the resonance of the chirality parameter. 2015-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/32298 In this work we propose a methodology to analyze the elastic energy interaction at the atomic level between Si self-interstitials and extended defects in crystalline Si. The representation of this energy in maps in 2D planes shows the anisotropic nature of the elastic interaction. This elastic energy maps can be used to understand diffusion trajectories of Si self-interstitials around extended defects obtained from classical molecular dynamics simulations. The combined analysis of these trajectories and the elastic energy maps shows preferential capture directions around extended defects. 2016-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/32297 The modeling of self-interstitial defects evolution is key for process and device optimization. For a self-interstitial cluster of a given size, several configurations or topologies exist, but conventional models assume that the minimum energy one is instantaneously reached. The existence of significant energy barriers for configurational transitions may change the picture of defect evolution in non-equilibrium processes (such as ion implantation), and contribute to explain anomalous defect observations. In this work, we present a method to determine the energy barriers for topological transitions among small self-interstitial defects, which is applied to characterize the Si self-interstitial and the di-interstitial cluster. 2017-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/32296 We performed a characterization of the energetic and structural features of amorphous Si using classical molecular dynamics simulations. We generated amorphous Si samples from different procedures: quenching liquid silicon, accumulating the damage generated by subsequent energetic recoils, and accumulating point defects. The obtained energetic and structural features of these types of samples are analyzed to elucidate which procedure provides a more realistic a-Si structure. 2017-01-01T00:00:00Z